Answer: I do believe the answer is, "to explain why there is a problem defining the first American novel".
Explanation: This doesn't define what american novels are.
There is only one mention of d'Auberteuil's novels, (actually it's only one novel) and it really doesn't explain what the paragraph is about.
The paragraph says nothing about how to classify American novels.
The first sentence states, "The argument continues about which novel has the honor of being the first American novel." So the Answer must be option two.